Data Structures and Algorithms in Java[1].pdf - Fulvio Frisone

In Figure 3.26, we show a recursion trace of a call to PuzzleSolve(3,S,U),
where S is empty and U = {a,b,c}. During the execution, all the permutations of the
three characters are generated and tested. Note that the initial call makes three
recursive calls, each of which in turn makes two more. If we had executed
PuzzleSolve(3,S, U) on a set U consisting of four elements, the initial call
would have made four recursive calls, each of which would have a trace looking
like the one in Figure 3.26.
Figure 3.26: Recursion trace for an execution of
PuzzleSolve(3,S,U), where S is empty and U = {a, b,
c}. This execution generates and tests all permutations
of a, b, and c. We show the permutations generated
directly below their respective boxes.
204